In the oil and gas industry, wellbores deviating from the vertical or perpendicular-to-the-surface plane to the horizontal plane have become increasingly common. Such horizontal or lateral wellbores are standard in hydrocarbon wells drilled into shale rock formations in the United States.
Many situations arise in complex lateral wells in which a conditional actuation of a downhole tool could be very beneficial, with whipstocks being a key example. When drilling a lateral well, it is necessary to place a whipstock in the wellbore so that a drilling bit may be directed out of the vertical plane and traverse into a horizontal—or relatively horizontal or lateral—plane. Anchoring systems, or “anchors,” are common in the industry, serving to hold the whipstock in place, either temporarily or permanently. Typically, anchors are actuated either mechanically or hydraulically. A mechanical anchor is simpler in design and function, actuating when it meets an obstruction, such as a bridge plug. When force applied through the workstring from the surface, a plunger at the bottom of the mechanical anchor is depressed into the anchor as it is pushed against the obstruction. Internal mechanisms extend slip(s) lock the anchor in place, extending outward from the anchor as the plunger depresses into the anchor.
In many cases, however, a more complex, hydraulically actuated anchor, is required. Many wellbores do not have casing in place or bridge plugs set prior to needing to set a whipstock. With nothing to push against, a hydraulic anchor, well known in the art, is employed. A general weakness of hydraulic anchor systems lies in the hydromechanical valve system(s) that actuate these anchors. The hydromechanical valve system generally performs a dual function, both closing circulation to the annulus (establishing flow through the drill string) and sending fluid and pressure to actuate the hydraulic anchor. Currently, such valve systems are triggered by increasing flow and pressure through the wellbore until a circulation closing and anchor actuating device moves. Wellbore debris, erosion, and “Measurement While Drilling” (MWD)/directional systems can complicate the function of such valve systems. Reliability issues are common. In the prior art, problems persist with setting an anchor too soon, i.e. at a higher depth in the wellbore than the target depth. In such cases, the whipstock and anchor must be pulled from the wellbore through application of great pulling force from the rig at surface, or otherwise circumnavigated through sidetracking or drilling a new wellbore.